Low spin double purpose mercury switch



Sept. 19, 1961 c, BROWN LOW SPIN DOUBLE PURPOSE MERCURY SWITCH Filed June 29, 1954 FIG.3.

FIGJ.

FIG.4.

FIG.2

INVENTOR C. F. BROWN TTORNEY United States Patei ltO 3,001,044 LOW SPIN DOUBLE PURPOSE MERCURY SWITCH Calvin F. Brown, Millersville, Pa., assignor to the United States of America as represented by the Secretary of the Navy Filed June 29, 1954, Ser. No. 440,306 4 Claims. (Cl. 200-80) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to mercury switches and more particularly to centrifugally actuated mercury switches suitable for use with a continuously rotating member and as an electrical fuzed projectile.

Moreover, the invention provides a new and improved mercury switch constructed and arranged to normally short an electroresponsive primer such, for example, as the type used in electrical and proximity fuzes and which will not be unshorted in response to a sudden shock.

Heretofore switches of this type have not proven entirely satisfactory particularly when used in electric fuzed projectiles for the reason that they may operate falsely in response to sudden shocks during handling and transpontation. They also lack the desired characteristics possessed by the device of the instant invention of operating at both high and low projectile spin such, for example, as when the projectile is propelled from the gun in response to either a full propellant charge or a half or greatly reduced propellant charge.

The present invention contemplates the provision of a new and improved switch which overcomes the aforesaid disadvantages encountered in prior art devices by providing a switch which is sufliciently rugged to withstand sudden and severe shocks without damage or actuation thereof and which will operate satisfactorily in a projectile propelled from a gun in response to a full propellant charge or a half propellant charge, as the case may be. The full charge is employed when the projectile is fired at an aircraft in flight and the half charge is employed when the projectile is fired at shore targets or the like which necessitate high trajectory of the missile. An object of the present invention is to provide a new and improved centrifugally actuated switch suitable for use in an electric fuze which is characterized by satisfactory timing relative to spin performance.

Another object of the invention is the provision of a centrifugal mercury switch which is responsive to either a low or high rate of spin.

A further object is the provision of new and improved means for preventing the operation of a mercury switch in response to a sudden shock and for controlling the rate of flow of the mercury while the switch is being continuously rotated about an optimum axis, not necessarily an axis through the switch.

Another object of the invention is the provision of a normally shorted centrifugal switch suitable for use in an electric fuzed projectile for arming an electroresponsive primer therein in predetermined time delay relation with respect to the firing of the projectile from the gun. A still further object of the invention is the provision of a normally shorted mercury switch wherein new and improved means are provided for controlling the rate of flow of the mercury from one chamber to another chamber in response to the spin of the switch thereby to unshort the switch when a predetermined period of time has elapsed.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following Patented Sept. 19, 1961 detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a view in elevation of the switch of the present invention;

FIG. 2 is a'sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken on the line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary elevational view of a projectile illustrating the manner in which the circuit controlling and delay switch may be mounted therein.

Referring now to the drawings wherein like reference characters indicate like parts throughout the several views thereof, the numeral 10 generally indicates the switch of the present invention. The switch comprises a cylindrical casing 11 having one end thereof sealed by a plug or bead 12 composed of any material suitable for the purpose such, for example, as glass or the like, the other end of the casing being flanged as at 13.

As more clearly shown on FIG. 2 a pair of mutually spaced electrodes 14 are sealed within the bead 12, one end of each electrode extending beyond the outer surface of the bead thereby to provide means for establishing an external electrical connection thereto, the other end of each electrode extending beyond the inner surface of the bead and into a chamber 15 formed between the bead and a delay unit generally indicated by the numeral 16. The chamber has sealed therein a quantity of mercury 17. i

The delay unit 16 is disposed between the flange 13 on casing 11 and a flange 18 formed on a sump or receiving container 18'. The aforesaid flanges 13-18 and the delay unit 16 are welded as at 19, FIG. 2, to provide an annular bead or sealing joint therebetween. Thus by this arrangement and the sealing plug arrangement 12 the mercury is hermetically sealed within the casing 11.

The delay unit 16 comprises a disc 21 composed of any material suitable for the purpose such, for example, as stainless steel or the like and having an annular flat rim 22 bordering on a centrally disposed crown or dishedshaped portion 23, the crown portion being provided with a centrally arranged opening 24. The surface of the rim 22 engaged by the mercury is highly polished and free from irregularities such, for example, as scratches, burrs and cavities and the opening 24 therein is small, an opening of substantially .0055 of an inch in diameter having been found satisfactory.

The delay unit also comprises a porous sintered disc or diaphragm 25 composed of any suitable metal such, for example, as stainless steel, the disc being provided with a circular fiat portion 26 bordering on a centrally disposed portion 27 of less density and greater porosity than a central portion '30. By the aforesaid disc arrangement it will be noted, FIG. 2, that a cavity 28 is formed between discs 21 and 25. The cavity is shallow, a depth of .002 to .005 inches having been found satisfactory.

It will be understood that the minute opening 24 in disc 21 functions to meter the flow of mercury from chamber 15 into cavity 28 when the switch is subjected to centrifugal force and thence the mercury is forced through the porous portion 27 of disc 25 by the aforesaid force. The sintered disc, however, functions to prevent flow of mercury into sump 18 in response to sudden and severe shock by its inability to instantaneously exhaust the air normally contained by the chamber 28 into the sump 18. The air normally contained in the cavity 28 therefore functions as an air cushion preventing mercury flow through the aperture 24 in response to a sudden impact force applied to the switch assembly 10. Moreover the cavity 28 between disc 2125 functions to receive the mercury forced through opening 24 in response to the aforesaid shock, the mercury being maintained therein for the duration of the shock by reason of the centrally disposed dense portion 30. However, When the shock wave has subsided, surface tension of the mercury in cavity 28 causes the mercury within the cavity to be forced back into chamber thereby restoring the switch to the initial condition. Moreover, the dense portion 30 of the disc functions to divert the perpendicular force of the mercury from orifice 24 into a parallel direction as a globule of mercury is forced through orifice 24 into cavity 28 in response to a sudden shock and thus since the component force is lacking the mercury will remain in the cavity. It will be understood, however, that when the pressure of mercury against porous portion 27 of disc 25 is sustained by centrifugal force as the projectile spins along its trajectory, the mercury will continue to flow from chamber 15 through aperture 24 into cavity 28 and thence through the less dense portion 27 of disc 25 into sump 18'. When a sufficient quantity of the mercury has been transferred from chamber 15 to sump 18' in the aforesaid manner the electrodes 14 are unshorted. By the aforesaid disc arrangement it will be understood that the mercury will not How through disc 25 in response to sudden and severe shocks. However, the mercury will readily flow through the disc when the device is subjected to centrifugal force by reason of the exhaustion of this air cushion through the more porous portion 26 of diaphragm 25.

In reference to FIG. 4 it will be noted that the switch 10 is illustrated in connection with a projectile 29, the switch being mounted therein in such a manner as to be readily operated in response to the spin of the projectile along its trajectory. Furthermore, the switch is adapted to be connected to an electroresponsive primer of any well-known type, for example, the pair of normally shorted electrodes 14 of the switch may be con nected to the usual pair of primary terminal respectively. By this arrangement it will be apparent that when the mercury in chamber 15 is reduced sufficiently to unshort the electrodes 14, the primer is adapted to be armed. The primer, however, is adapted to be armed a predetermined period of time after the projectile has been fired from a gun such, for example, as /2 of a second, the time period being controlled by the rate of fiow of the mercury through the aforesaid delay unit 16.

Briefly stated in summary, it will be apparent that. a new and improved mercury switch has been devised for use in an electrical fuzed projectile which will operate in response to either a relatively low or high rate of spin of the projectile thereby to arm the usual electroresponsive primer and which will withstand repeated shocks without operation of the switching elements.

While the present invention has been described in connection with a spin projectile, it will be understood that if desired the switch may be employed for delaying the operation of numerous electrical devices and elements.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed as new and desired to be secured by Letters Patent in the United States is:

l. A switch of the character disclosed comprising a hermetically sealed casing, a disc disposed within the casing substantially midway between each end thereof thereby to provide two chambers, a quantity of mercury disposed in one of said chambers, a pair of electrodes disposed in said one chamber and normally shorted by said mercury, orifice means in said disc for controlling the rate of flow of the mercury, a sintered element having an annular porous portion formed therewith through which the mercury passes from said one chamber to the other chamber in a sufiicient quantity to unshort said electrodes when the pressure of mercury against said porous portion is sustained for a predetermined period of time by centrifugal force, a centrally disposed dense portion formed with and enclosed by said porous portion and concentric with said orifice means for diverting the mercury sufficiently to prevent the mercury from entering said other chamber as the mercury is forced through said orifice against said dense portion in response to a sudden shock, and a crown on said disc forming a cavity between said disc and element in communication with said orifice means for receiving and maintaining the mercury forced through said orifice means until said shock has subsided.

2. A mercury switch of the character disclosed comprising a hermetically sealed casing, a disc and a sintered element disposed within and sealed to said casing midway between each end thereof for providing two chambers, a quantity of mercury disposed in one of said chambers, a pair of electrodes disposed within said one chamber and normally shorted by said mercury, orifice means in said disc in communication with said one chamber and spaced from said sintered element for controlling the rate of flow of the mercury from the chamber, an annular porous portion formed with said sintered element through which the mercury passes from said one chamber to the other chamber when the pressure of the mercury against said porous portion is sustained by centrifugal force thereby to reduce the mercury in said one chamber sufiiciently to unshort said electrodes, a centrally disposed dense portion formed with and enclosed by said element for diverting the mercury sufiiciently to prevent the mercury from entering said other chamber as the mercury is forced through said orifice means in response to a sudden shock, a crown on said disc forming a cavity between said disc and element in communication with said orifice means for receivin and maintaining the mercury forced through said orifice means until said shock has subsided.

3. A mercury switch comprising a hermetically sealed casing having a quantity of mercury disposed therein, an apertured disc disposed Within said casing, a second disc in abutting subadjacency with said first named disc, said discs having a chamber formed therebetween, an annular porous element forming a portion of said second disc and being characterized to pass said mercury under a high sustaining pressure, and a centrally disposed dense portion forming a part of said second disc and enclosed by said annular element for preventing passage of said mercury through said second disc as the switch is subjected to a sudden shock.

4. A mercury switch comprising a hermetically sealed casing having a pool of mercury disposed therein, a disc disposed within said casing and having a centrally disposed aperture therein, a sintered member in abutting relationship With said disc and having an annular porous element carried thereby for passing mercury under a high sustaining pressure, a centrally disposed dense portion forming a part of said sintered member and concentn'c with said orifice for preventing passage of said mercury through said member when the mercury is forced through said orifice in response to a sudden shock received by said switch, and a crown on said disc forming a cavity between said disc and member for receiving and maintaining the mercury forced through said orifice until said shock has subsided.

References Cited in the file of this patent UNITED STATES PATENTS 2,414,836 Rickmeyer Jan. 28, 1947 2,435,602 Rickmeyer Feb. 10, 1948 2,435,603 Rickmeyer Feb. 10, 1948 2,436,601 Rickmeyer Feb. 24, 1948 2,509,527 Rickmeyer May 30, 1950 

